1. Field of the Invention
The present invention relates to a line contour enhancement circuit for enhancing line contours of video images.
2. Description of Background Information
Line contour enhancing circuits are widely used for improving sharpness of television images. Conventionally, a method has been used in which a second order differentiation operation is effected to a video signal and the generated second order differentiation signal is added to the video signal.
On the other hand, if a dark scene is televised by a video camera, the S/N ratio of the video signal is generally degraded in dark portions of the image. Therefore, when a conventional line contour enhancing process is effected to a signal having a low luminance level, it increases noises in the reproduced image. So there has been a problem that picture quality is degraded.